Endemic goiter in the Cauca Valley. I. Results and limitations of twelve years of iodine prophylaxis.

Abstract

The effects of iodine prophylaxis on the endemic goiter of the Cauca Valley, Colombia, S. A., were investigated by a longitudinal epidemiologic study carried out in school and general populations during an 8-yr period. The results obtained were compared with observations made prior to iodine prophylaxis, which was begun in 1955. Before the iodization program was started, statistically significant differences existed in the prevalence rates of goiter in towns near one another. Once iodine prophylaxis was established, we found: 1) a marked decrease in the percentage frequency of goiter in the towns with high rates, but no change in those with low rates; 2) constant and fixed prevalence rates of goiter of around 30% in school and adult populations of Candelaria in the Cauca Valley during the past 8 yr while on an adequate and uniform iodine supplementation as documented by consistently high urinary iodine excretions, low normal thyroidal 131I uptakes and sufficient iodine content of the salt; 3) an incidence or attack rate of goiter in school children of 12.8% for an 8-month period; 4) the absence of goiter during the first 5 yr of age and its subsequent appearance while taking iodine; 5) the development of goiter in children born while there was an appropriate maternal iodine intake; and 6) a statistically significant difference in the percentage frequency of goiter between school children of similar age distribution, socioeconomic status and urinaiy iodine excretions but living 20 miles apart. These facts provide evidence to support the thesis that the goiter endemia that is still present in Candelaria in the Cauca Valley is not responsive to an adequate iodine supplementation and therefore must be caused by factors other than a state of iodine deficiency. The conditioning influence of iodine on the over-all magnitude of the problem and of age and sex in the development, relative frequencies and persistence of goiter is discussed and the possibility of “goitrogenic” substances as causative factor(s) of the Cauca Valley endemia is postulated.